Previous arts of suction aspirators consist of a suction tube with or without an interrupting valve. These valves are mainly incorporated to control the vacuum suction flow and obviously, the control of suction noise is inefficient.
U.S. Pat. No. 2,650,792 by Marco (C1L2,3) "A valve employed for controlling flow of a liquid or semi-solid materials". (C5-L58): "A valve for mixing apparatus . . . . " U.S. Pat. No. 3,998,227 by Holbrook et al: (C1-L65,66): "A new and improved regulator for fluids aspiration systems" from which the suction noise is not completely eliminated: (C2-L12,13: "A minimum or no noise generating capacity".
U.S. Pat. No. 4,610,664 by Harle: (C2-L46,47,48,49) using different valve mechanism mainly for one-handed operation.
U.S. Pat. No. 3,517,669 by Bouno et al: (C1-L13,14): "A valve for eliminating suction forces at a catheter tip". (C4-L1,2): "even the catheter port is closed, the atmospheric port is open to the suction source".
U.S. Pat. No. 3,335,727 by Victor T Spoto: "A valve controlled suction device through which the flow of blood may be controlled", (C3-L14,15): "The provision of a vent passage on the downstream side of the valve assembly".